The present invention relates generally to a beach for the scum trough of a sewage settling tank or the like. Such beaches are well known in the art and are used to prevent a continuous flow of liquid from the sewage settling tank over into the scum trough. In one scum trough design, the upper edge of the trough is located above the level of liquid in the tank and the beach is a rigid structure inclined downward from the top of the trough into the liquid. With this arrangement, a wiper may scrape any floating material up the inclined beach and over into the trough. British patent specification No. 390,989 illustrates such an arrangement.
In another design an upper edge of the scum trough is located below the level of liquid in the settling tank. The beach here is hinged to the upper edge of the scum trough and is provided with floats to permit the beach to float above the level of liquid in the settling tank and this prevents the liquid in the settling tank from spilling over into the scum trough. The floating beach can be forced to submerge whenever necessary to permit accumulated scum or other floating materials to flow over the submerged beach and into the scum trough. Such an arrangement is shown, for example, in U.S. Pat. No. 4,054,520.
Both of the beach designs described have disadvantages. For example, where a fixed beach is used, a wiper or scraper of one sort or another must be pushed up the fixed beach and out of the level of liquid in the settling tank. Where a floating beach is used, the wiper need not leave the level of liquid in the settling tank, but on the other hand the build up of deposits upon the beach over a period of time will hamper its operation.